The present invention relates to a mat for the cultivation of plants, and to a method of improving soil as by controlling soil erosion with a mat.
It has been recognized that the growth of plants, such as grass, may be enhanced by the provision of mats which comprise support medium for seeds, and which are placed upon the ground. These mats, either before or after placement on the ground, are provided with seeds, which may be watered, fertilized, etc., so as to promote the rapid germination of the seeds and rapid plant growth.
Among the proposals which have been made for mats of this type is Allen U.S. Pat. No. 2,923,093, which provides a seed planting mat having a bottom layer of loosely matted fibers to form a porous foundation, the fibers being either interwoven or unwoven; on top of this layer is a layer of growing media, containing fertilizers, mulch, and seeds, and this layer is covered with a cover layer of loose fibers matted together and which may be either natural fibers, synthetic, plastic, or glass wool. The three layers are felted together, and the resulting mat is capable of being stored and transported, and then applied to a field for plant growth. The resulting mat is of lesser strength than is desirable, due to the structural layer being laterally unstable under loads imposed during handling and placement.
Gidge U.S. Pat. No. 4,062,145 discloses a mulch mat or carpet in which a woven plastic mesh layer is provided between upper and lower layers formed of ground bark particles unified and individually encapsulated in a resin binder. The woven mesh is not dimensionally stable.
Muldner U.S. Pat. No. 4,190,981 and Muldner United Kingdom Application 203,301 provide a mat for growing lawns including a lower base sheet comprising a biodegradable web, a bed of seeds and dried compressed peat particles thereon adhesively secured to the base sheet, and an upper layer or veil of unwoven web material adhesively secured to the bed. Muldner U.S. Pat. No. 4,318,248 provides a mat of this type in which there are provided a lower base sheet of biodegradable we material, and a seed bed thereon including seeds, dehydrated gel material and dried peat particles, the seed bed secured to the base sheet, and an upper veil of non-woven porous web material. These mats are deficient in that they are not as strong as desirable, for handling and transporting and are also dimensionally unstable.
Mercer U.S. Pat. No. 3,845,584 provides a method of growing grasses in which there is provided a net or mesh layer which is held above and bonded to a root impermeable base, the structure being laid upon the ground, followed by the application of seed and growth medium.
German Patent 2,150,770 provides a seed carpet in which seed is provided between upper and lower layers of material.
Pratt U.S. Pat. No. 1,971,504 provides a mat having a disintegrable backing or reinforcement having thereon a water soluble fertilizer and seeds, with the seeds being adhered in position, but spaced from the fertilizer by a breaker strip of flexible material which functions to keep the acidity of the fertilizer from adversely affecting the seeds. The backing layer is preferably of cotton knitting or may be paper with reinforcing threads, and this lacks strength and structural stability.
Tietz et al U.S. Pat. No. 2,876,588 provides a grass mat including a lower layer of impervious material such as a plastic sheet, a layer of burlap on the plastic sheet, a layer of peat moss, seeds on the peat moss layer, and optionally a further layer of peat moss. A further plastic film is provided over the top, and the entire assemblage may be rolled for transportation. The mat has less strength than is required.
Surowitz et al U.S. Pat. No. 4,219,600 discloses a moisturizing mat made by depositing wood pulp fibers on a fibrous layer, then placing a second fibrous layer thereon, followed by bonding the second layer or web to the first, and then bonding an impervious plastic film to one surface of the resulting product.
Baron U.S. Pat. No. 4,364,197 provides a method of making pregrown turf in which a layer of grass seeds is sandwiched between two layers of non-woven cloth, one of which is made of flax fibers, there being optionally included polystyrene particles between the layers. The layers may be placed on a plastic sheet.
King et al U.S. Pat. No. 4,309,844 provides a mat in which a layer of seeds is provided between a pair of polyurethane foam sheets: a reinforcing net-like layer may be provided between the polyurethane foam sheets. The polyurethane sheets are adhered together by fusion from flame lamination.
The hereinabove disclosed mat structures are deficient in providing a mat for growing grass which is of relatively great strength, permitting after-fabrication handling and/or rolling for transportation and storing, and then being laid out on the ground, together with a structure which will enable water to penetrate to the seeds, and which will protect the seeds from being eaten by birds, while providing a mulch.
It has heretofore been proposed to provide various constructions of mats to the soil for preventing erosion. German patent 1,126,633 discloses the use of a sod mat, with grass already growing, for placement onto bare ground, as on a hillside. Such a mat is extremely heavy and is therefore difficult to transport and to apply.
Pratt U.S. Pat. No. 1,971,504 provides a mat which includes a base of reinforced paper or cotton netting surmounted by fertilizer, a flexible breaker strip, surmounted by seeds adhered to the breaker strip by suitable adhesive. The structure may be rolled, but lacks strength and lacks porosity, as well as permits the seeds to be exposed so that many of the seeds may be eaten by birds.
Gidge U.S. Pat. No. 4,062,145 provides a mulch carpet comprising a plastic mesh intermediate layer and upper and lower layers formed of ground bark particles encapsulated in resin binder which adheres the bark particles to each other and to the mesh. The porosity of the mat is such that plant growth is inhibited.